Games of 2010: Super Mario Galaxy 2

Mario Galaxy 2 is a series of dizzying anecdotes, sugar dreams and hallucinogenic episodes condensed into tiny, full-to-bursting vignettes. There's the strangely terrifying experience of being dogged by endless replays of your own thoughts in the form of Shadow Marios, there's the celebratory nostalgia of the Throwback Galaxy, there's the taut, tense self-control of the Flip-Swap Galaxy and the breakneck thrill of a Tall Tree speed run - and none of it lasts more than five minutes. It never settles for a second, guiding you by the elbow from novelty to novelty at a breathless pace, always pointing excitably towards its next new idea.

It's so well-made, too. That's an obvious thing to point out about a Nintendo game, but it's easy to forget. After a while, you take the solidity and precision of these worlds for granted. There's such a gorgeous physicality to everything: Yoshi's flicking tongue, the chime of coins, big, chunky switches, Mario's spin, and of course Mario himself, who leaps, runs, skids and cartwheels with as much playful athleticism as ever.

Despite Super Mario Galaxy's desire to lavish entertainment upon you, it doesn't give itself up easily. It's a hard game, packed with secrets, and always perfectly fair. There's never more than a moment of congratulation before you're moved on to something more difficult. Over the course of Mario Galaxy 2, you see its worlds again and again, but every new star or prankster comet gives them a new face, often turning your expectations and experience against you with a cackle. Dangerous, high-speed races become exacting purple coin challenges, colourful playgrounds become demanding speed-runs, Green Stars hide in nooks that you didn't know existed. It's always remixing itself as well as Mario history, continually reinventing on the spot.

It's embarrassing how many ideas it has. Sometimes, in its very best moments, Super Mario Galaxy 2 seems to exist on a separate plane from everything else. This year has been the best in my memory for games I've loved - Bayonetta, Mass Effect 2, Heavy Rain and Red Dead Redemption have all reinforced my faith in this as the most startlingly diverse, stimulating field in all of entertainment, and in any other year I may well have been writing about Deadly Premonition as my personal favourite. I certainly didn't expect my defining game of the year to come from a series that I've known intimately for so long. After two and a half decades, the Mario series still fizzes with a breathless sense of possibility.

So why did I only realise that Super Mario Galaxy 2 was my favourite game of all time 30 seconds into the Throwback Galaxy? It wasn't simply because it showed me an emotionally charged moment from my own gaming history - it had already blown me away with its inventiveness. But it was then that I realised that Mario, in many ways, is what videogames are to me, what they've been to me since my childhood. They're imagination, playfulness, creativity, inclusiveness, fun, challenge. They're unexplored worlds.

I realised, at that moment, that Mario Galaxy 2 is my definition of a videogame - or rather, the definition of what I'd like videogames to be.